CTSK and osteoarthritis, knee: Cathepsin K (encoded by the CTSK gene) is an enzyme that plays a critical role in collagen degradation within osteoclasts, and MIV-711 is a selective cathepsin K inhibitor that has recently been shown in a phase 2 clinical trial to be effective in reducing structural damage in patients with knee osteoarthritis (Conaghan et al., 2020).